The lamp compartment is sealed to IP66 and uses a 'Filterseal' system to seal the reflector against the lens, thus keeping the compartment watertight. C U Phosco's publicity for the lantern states: 'A FILTERSEALED lantern is one which is sealed to IP65 or above and also incorporates an activated charcoal filter. The special granules of activated charcoal have many thousands of tiny pores. One gram of these tiny particles has an internal surface area as great as two tennis courts. As air passes through the carbon it acts as a highly efficient filter trapping even microscopic traces of contaminants'.

Cut off versions of the P678. Photos: CU Phosco Ltd

The lantern in the collection was acquired on 5th Decmeber 2006 and had come from a scheme in Leicestershire, where P678's had been used in the ad-hoc replacement of aging MRL6's, but had then themselves been ousted by a Urbis Sapphire-2's. lanterns.

Underside view of the CU Phosco P678 lantern showing the control gear access panel and position of the 150w SON-T lamp.

 P678 lantern in profile with its Cableform SS6 photocell.

The stainless steel locking device at the front of the lantern holds the lamp compartment in position against the canopy.

The lamp compartment opened and positioned in the vertical attitude for lamp changing.The lamp is changed by means of a bayonet arrangement lampholder device, similar to that of the Thorn Alpha 2000, which simply twists to unlock the unit from the lantern . However, unlike the Alpha 2000, the arrangement is such that the lampholder faces towards the ground during lamp change overs to reduce the possibility of ingress of water or other materials during lamp changing. The problem with this particular lantern is that the wires to the lamp holder aren't long enough to allow for the removal of the lamp holder and lamp in the vertical position, so the compartment has to be hinged upwards to leave enough slack in the wiring to pull the lamp clear of the refector unit.

Removal of the twist-lock lampholder unit, showing the nice clean interior.

Access door to the gear compartmet opened. The control gear is attached to the door, so it also acts as the gear tray and has a quick-release hinge to allow rapid change-over of the control gear as a single unit.

The quick-release gear tray removed and upturned to show the Philips 150w HPS ballast, ignitor and capacitor layout. Despite the high ingress protection rating for the lamp compartment, the gear compartment doesn't look to have faired as well.

With the Phosco label peeled back, the GE heritage of the lantern is revealed.

Leicestershire County Council CU Phosco P678's at Sawley on the Leicestershire/Derbyshire border in December 2006.